UC-NRLF 


ROSS 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


LABORATORY  GUIDE 

IN 

MARKET  MILK 


BY 

H.  E.  ROSS, 

Professor  of  Dairy  Industry,  New  York  State  College  of  Agriculture 
at  Cornell  University 


1915 

CARPENTER  &  CO. 
ITHACA.  N.  Y. 


COPYRIGHT 
1915 

CARPENTER  &  Co. 


PRESS  OF  W.  F.  HUMPHREY,  GENEVA,  N.  Y. 


PREFACE 

The  production  and  handling  of  clean  milk  is  based  on  scientific 
principles.  It  is  true  that  many  of  these  principles  are  simple  in  their 
application  and  oftentimes  on  account  of  their  simplicity  they  are 
overlooked  and  neglected.  It  is  the  purpose  of  this  laboratory  guide 
to  enable  the  student  to  better  understand  the  application  of  science 
to  clean  milk  production,  and  to  impress  on  his  mind  the  necessity  for 
attention  to  detail  in  this  branch  of  Dairy  Industry. 

Our  ideas  concerning  the  best  methods  of  clean  milk  production 
are  constantly  changing.  The  Author  recognizes  that  this  will 
necessitate  frequent  revision  of  this  book  and  an  effort  will  be  made  to 
keep  this  laboratory  guide  thoroughly  up-to-date. 

H.  E.  Ross. 

Dairy  Laboratories 

New  York  State  College  of  Agriculture  . 
at  Cornell  University 
Sept.  14,  1915 


It  is  generally  accepted  that  clean  milk  means  milk  which  is  free 
from  microorganisms  or  the  products  of  their  action.  It  is  possible 
to  conceive  of  milk  being  impure  from  something  other  than  micro- 
organisms or  their  products,  such  as  the  addition  of  some  poisonous 
substance  to  milk.  The  possibility  of  such  contamination  is,  however, 
so  rare  and  so  remote  that  the  words  "impure  milk,"  have  come  to 
mean  that  which  is  affected  by  the  action  of  microorganisms. 

For  this  reason  all  operations  and  experiments  performed  in  a 
laboratory  should  be  done  in  such  a  way  as  to  prevent  bacterial  con- 
tamination, and  all  dairy  utensils  with  which  the  milk  comes  in  con- 
tact should  be  rendered  sterile  so  far  as  possible.  This  can  be  done 
by  thoroughly  scalding  all  dairy  apparatus,  or  better  still  by 
exposing  them  to  live  steam  for  not  less  than  one  hour.  If  the 
dairy  utensils  are  scalded  by  means  of  hot  water,  the  temperature  of 
the  water  should  be  not  less  than  i8o°F.  and  it  should  be  as  near  the 
boiling  point  as  possible. 

Dippers  and  other  dairy  utensils  in  which  milk  is  handled,  or  which 
comes  in  contact  with  the  milk  in  any  way,  should  not  be  laid  on  the 
floor  and  then  placed  in  the  milk.  Care  should  be  taken  not  to  touch 
the  surfaces  of  dairy  utensils,  such  as  coolers,  bottle  fillers  and  so 
forth,  with  the  hands.  Water  even  in  small  amounts,  may,  if  allowed 
to  enter  milk,  cause  it  to  putrefy. 

CLEANING  DAIRY  UTENSILS 

Dairy  utensils  must  be  thoroughly  cleaned  if  milk  is  to  be  handled 
in  a  sanitary  manner.  The  proper  way  in  which  to  clean  a  dairy 
utensil  is  to  first  rinse  it  with  cold  or  luke-warm  water,  preferably  the 
latter.  This  removes  most  of  the  milk  from  the  utensil  and  prevents 
later  cooking  of  the  albumen  of  the  milk  on  to  the  apparatus,  when  it 
is  scalded  or  sterilized.  The  utensil  should  next  be  thoroughly  washed 
by  means  of  a  brush  and  hot  water  in  which  there  has  been  dissolved 
some  good  washing  powder.  An  excessive  amount  of  powder  is  not 
necessary,  a  tablespoonful  to  a  pail  of  hot  water  is  usually  sufficient. 
The  utensil  should  then  be  scalded  in  hot  water,  and  if  possible, 
exposed  to  the  action  of  live  steam  for  not  less  than  one  hour,  thereby 
rendering  the  utensil  as  sterile  as  possible.  It  should  be  kept  in  a 
place  where  it  will  not  become  recontaminated. 


EXPLANATION   OF  EXERCISE   I 

In  studying  any  dairy  utensil,  it  should  be  noted  whether  the  uten- 
sil is  so  arranged  and  constructed  as  to  best  fulfill  the  purpose  for 
which  it  is  intended.  All  dairy  utensils  should  be  as  simple  as  possible 
in  construction.  They  should  have  no  seams  and  crevices  into 
which  milk  can  collect.  Any  cracks  or  seams  in  copper  or  tin 
surfaces  should  be  well  flushed  with  solder.  All  parts  should  be 
accessible  so  that  they  may  be  thoroughly  cleaned.  They  should 
be  strong  and  durable  and  at  the  same  time,  any  extra  metal  or  other 
material  is  objectionable.  On  account  of  its  durability  and  the  ease 
with  which  it  may  be  cleaned,  metallic  is  usually  preferable  to  wooden 
construction. 

When  possible,  metallic  construction  should  be  of  some  non-rusta- 
ble  material. 

EXERCISE   I 
A  STUDY  OF  DAIRY  APPARATUS 

1.  Bottle  Fillers — Study  the  tubes  of  the  different  fillers  used. 
Show  by  drawings  how  the  milk  flows  from  the  tank  through  the  tube 
into  the  bottle,  and  the  provision  made  for  removing  air  and  surplus 
milk  from  the  bottle. 

Pasteurizers — Show  by  cross-sectional  drawing  the  method  of 
operation  of  a  holder  pasteurizer  and  a  flash  pasteurizer. 

2.  Clarifiers — Explain  the  action  of  a  centrifugal  clarifier.     In 
each  case  show  by  means  of  a  drawing  the  chief  differences  between 
the  inner  device  of  the  clarifier  and  a  cream  separator  of  the  same 
make.     Also  compare  the  relative  speed  of  clarifiers  and  separators 
of  the  same  make  and  having  the  same  capacity  per  hour. 

3.  Coolers — Make  drawings  of  a  conical  and  tubular  type  of 
cooler  and  explain  the  action  of  each. 

In  case  of  the  tubular  cooler,  show  its  connection  with  a  brine 
barrel  and  indicate  the  relative  position  of  the  cooler,  brine  barrel  and 
pump. 

4.  Milk  Bottles — Make  drawings  of  two  different  styles  of  milk 
bottles. 


DIRECTIONS   FOR  STANDARDIZATION 

The  process  of  standardization  consists  in  raising  or  lowering  the 
percentage  of  fat  in  milk  or  cream  to  a  definite  standard.  This  is 
done  by  adding  milk  of  a  higher  or  lower  fat  content,  than  the  material 
which  is  being  standardized. 

Some  market  milk  does  not  normally  contain  sufficient  fat  to  be 
satisfactory  to  the  consumer.  In  order  to  make  this  milk  satisfactory 
the  dealer  oftentimes  standardizes  it  by  the  addition  of  cream. 

Since  the  law  states  that  unadulterated  milk  is  milk  to  which 
nothing  has  been  added  or  anything  taken  away,  there  has  been 
raised  some  slight  question  as  to  the  legality  of  the  process  of  stand- 
ardization. However,  the  addition  of  cream  to  milk  increases  its 
value,  so  that  no  serious  objection  has  been  raised  to  that  part  of  the 
process.  One  would,  however,  have  no  right  to  reduce  the  fat  con- 
tent of  milk  by  the  addition  of  skimmed  milk,  as  this  would  be 
essentially  the  same  as  removing  fat  from  the  milk. 

At  the  present  time  much  of  the  cream  sold  is  paid  for  on  a  basis 
of  its  fat  content  and  for  this  reason  a  knowledge  of  standardization  is 
useful  to  the  cream  shipper.  If  a  dealer  receives  a  certain  price  for 
cream  containing  a  definite  percentage  of  fat  it  is  desirable  to  have  no 
more  or  no  less  fat  than  the  percentage  agreed  upon.  If  there  is  more 
fat  than  the  contract  calls  for,  the  seller  loses,  and  if  there  is  less  fat 
the  buyer  loses. 

In  standardization  there  are  two  classes  of  problems  involved: 
first,  one  in  which  two  products  containing  a  known  percentage  of  fat 
are  mixed  to  make  a  definite  amount  of  milk  or  cream  containing  a 
fixed  percentage  of  fat,  and  second,  one  in  which  a  definite  amount  of 
milk  or  cream  of  a  known  percentage  of  fat  is  used  and  enough  of  some 
other  product  added  to  make  the  resulting  mixture  test  the  desired 
percentage  of  fat.  In  the  first  case  the  amount  is  definite,  and  in  the 
second  case  it  is  indefinite. 

The  usual  method  of  working  standardization  problems  is  quite 
difficult,  but  Pearson  has  devised  a  method  which  greatly  simplifies 
the  computation.  It  is  as  follows:  Draw  a  rectangle  and  place  in 
the  center  of  it  the  percentage  of  fat  desired.  On  the  left  hand 
corners  place  the  percentages  of  fat  in  the  materials  to  be  mixed.  It 
is  customary  to  place  the  larger  percentage  on  the  upper  left  hand 
corner  and  the  smaller  percentage  on  the  lower  left  hand  corner, 

8 


although  the  position  of  these  numbers  might  be  reversed  without 
affecting  the  results.  Subtract  the  smaller  number  on  the  left  hand 
corner  of  the  rectangle  from  the  number  in  the  center  and  place  the 
remainder  on  the  diagonally  opposite  right  hand  corner.  Then  sub- 
tract the  number  in  the  center  of  the  rectangle  from  the  larger  number 
on  the  left  hand  corner  and  place  the  remainder  on  the  diagonally 
opposite  right  hand  corner.  The  two  numbers  on  the  right  hand 
corners  of  the  rectangle  represent  the  number  of  pounds  of  materials 
required.  The  sum  of  these  two  numbers  will  be  a  mixture  containing 
the  desired  percentage  of  fat,  expressed  by  the  number  in  the  center 
of  the  rectangle. 

In  each  case  the  number  on  the  right  hand  corner  of  the  rectangle 
corresponds  to  the  number  on  the  left  hand  corner  directly  opposite. 

A  few  concrete  examples  will  illustrate  the  rectangle  method  of 
working  problems  in  standardization. 

Problem  I.  How  many  pounds  of  23 %  cream  and  3 %  milk  will  be 
required  to  make  500  pounds  of  an  18%  cream?  Using  our  diagram 
as  described  above  we  have  the  following  results: 


18 


15-' 


These  results  mean  that  if  five  pounds  of  3%  milk  were  mixed  with 
15  pounds  of  23%  cream  the  result  will  be  20  pounds  of  a  mixture 
testing  1 8%.  The  amount  of  the  mixture  desired  was  500  pounds, 
which  is  twenty-five  times  the  amount  obtained  with  the  rectangle 
method  (500 -r-  20  =  25).  If  we  multiply  the  numbers  on  the  upper 
and  lower  right  hand  corners  of  the  rectangle  by  twenty-five  we  will 
obtain  respectively  the  pounds  of  23%  cream  and  3%  milk  required 
to  make  500  pounds  of  an  18%  mixture.  These  are  375  pounds  of 
23%  cream  (15  x  25  =  375),  and  125  pounds  of  3%  milk  (5  x  25  = 
125). 

The  problem  may  also  be  worked  by  simple  proportion: 
5:20     ::    X     :     500 

2OX    =    25OO 

X  =  1 2  5  pounds  of  3  %  milk. 
15:20     ::     X     :     500 

2oX  =  7500 
X  =  375  pounds  of  23%  cream. 


IO 


In  the  above  problems  the  amount  of  the  mixture  desired  is 
definite. 

In  working  problems  in  standardization  it  is  wisest  to  prove  the 
answer  as  this  will  show  if  the  results  are  correct.  While  proving 
a  problem  will  point  out  errors  it  will  not  show  where  mistakes  have 
been  made.  The  proof  of  the  above  problem  is  as  follows: 

Proof: 

It  is  desired  to  make  500  pounds  of  an  18%  mixture  which  would 
necessarily  contain  90  pounds  of  fat  (500  X  .18  =  90).  According  to 
our  computations  the  500  pounds  of  18%  cream  will  consist  of  125 
pounds  of  3  %  milk  and  375  pound  s  of  2  3  %  cream .  If  these  material  s 
furnish  90  pounds  of  fat,  the  problem  is  worked  correctly.  One 
hundred  twenty-five  pounds  of  3%  milk  will  contain  3.75  pounds  of 
fat:  (1.25  X  .03  =  3.75).  Three  hundred  seventy-five  pounds  of 
23%  cream  will  contain  86.25  pounds  of  fat  (375  X  .23  =  86.25), 
86.25  +  3-75  =  90  pounds  of  fat. 

In  the  following  problem  the  amount  of  mixture  to  be  made  up 
is  indefinite. 

Problem  2: 

How  much  23%  cream  must  be  mixed  with  500  pounds  of  3%  milk 
to  make  a  mixture  testing  1 8%  ?  Using  our  diagram  according  to  the 
directions  previously  given  we  have  the  following  results: 


£3' 


18 


15- 


5-. 


These  results  mean  that  we  must  mix  the  materials  in  the  proportion 
of  15  pounds  of  23%  cream  to  five  pounds  of  3%  milk  to  make  an 
1 8%  mixture.  According  to  the  conditions  of  the  problem  we  must 
use  500  pounds  of  3%  milk  which  is  100  times  as  large  as  the  amount 
given  in  the  above  proportion  (500  -=-  5  =  100).  The  23%  cream  and 
the  3%  milk  must  be  kept  in  the  proportion  of  15:5  and  if  the  3% 
milk  is  increased  one  hundred  times  the  23%  cream  must  be  increased 
the  same  number  of  times.  This  would  give  1500  pounds  of  23% 
cream  (15  X  100  =  1500),  which  should  be  added  to  the  500  pounds 
of  3%  milk,  giving  2000  pounds  of  an  18%  mixture.  The  problem 
may  also  be  worked  by  simple  proportion. 


15      :     5      "     X     :     500 
5X  =  7500 

X  =  1 500  pounds  of  23%  cream. 
Proof: 

The  2000  pounds  of  18%  cream  will  contain  360  pounds  of  fat 
(2000  X  -18  =  360).  According  to  our  results,  the  2000  pounds  of 
1 8%  cream  is  made  up  of  500  pounds  of  3%  milk  and  1500  pounds  of 
23%  cream.  The  500  pounds  of  3%  milk  will  contain  15  pounds  of 
fat  (500  X  .03  =  15).  The  1500  pounds  of  23%  cream  will  contain 
345  pounds  of  fat,  345  +  1 5  =  360  pounds  of  fat,  which  is  the  number 
of  pounds  in  the  mixture. 

In  the  original  method  of  working  problems  in  standardization  all 
computations  are  made  on  a  pound  basis.  From  this  basis  it  is  easy 
to  compute  the  amount  of  different  materials  needed  to  make  up  any 
given  quantities  of  milk  or  cream.  Problems  are  worked  by  this 
method  as  follows: 
Problem  3. 

How  much  23%  cream  must  be  mixed  with  500  pounds  of  3%  milk 
to  make  a  mixture  testing  18%? 

One  pound  of  23%  cream  will  contain  .23  pounds  of  fat. 
One  pound  of   3%  milk  will  contain      .03  pounds  of  fat. 

The  difference  is 20  pounds  of  fat. 

Every  time  one  pound  of  .23%  cream  is  removed  and  a  pound  of 
3%  milk  substituted  there  is  removed  .20  pounds  of  fat. 
One  pound  of  23%  cream  contains  .23  pounds  of  fat. 
One  pound  of  18%  cream  contains  .18  pounds  of  fat. 

The  difference  is 05  pounds  of  fat. 

It  is  desired  to  reduce  the  fat  content  .05  pounds  of  fat  for  every 
pound  of  the  mixture.  This  is  done  by  the  addition  of  3%  milk 
which  may  in  this  case  be  regarded  as  a  reducing  agent.  Since  the 
substitution  of  a  pound  of  3%  milk  for  a  pound  of  23%  cream  reduces 
the  fat  content  of  a  pound  mixture  .20  pounds  of  fat  and  it  is  desired 
to  reduce  the  fat  content  .05  pounds  of  fat,  it  will  require  as  much 
of  the  3%  milk  as  .20  is  contained  into  .05  or  .25  (.05  -r-  .20  =  25). 
The  .25  is  the  number  of  pounds  of  3%  milk  there  would  be  in  one 
pound  of  an  1 8 %  mixture .  The  remainder . 7 5  pounds  (i  —  .25  =  .75), 
would  be  23%  cream.  The  following  simple  proportion  will  give  the 
number  of  pounds  of  23%  cream  which  must  be  added  to  500  pounds 
of  3%  milk  to  make  a  mixture  testing  18%  fat. 


12 

.75     :.as     :     :    X     :     500 
•25  X  =  375 
X  =  1 500  pounds  of  23%  cream. 

The  following  problem  is  an  illustration  of  the  original  method 
of  working  standardization  problems  when  a  definite  amount  of  the 
mixture  is  desired. 
Problem  4. 

How  much  23%  cream  and  3%  milk  must  be  mixed  to  make  a 
cream  testing  18%?  Since  the  percentages  of  fat  in  these  problems 
are  the  same  as  those  in  Problem  3,  the  amount  of  3%  milk  in  one 
pound  of  an  18%  mixture  would  be  the  same  as  already  shown,  and 
therefore  needs  no  further  explanation.  Since  .25  is  the  number  of 
pounds  of  3%  milk  in  one  pound  of  18%  cream,  we  would  have  the 
simple  proportion: 
i:.25  ::  500  :  X 

X  =  125,  the  number  of  pounds  of  3%  milk  in  an  18%  mixture. 
The  remainder  of  the  mixture,  375  pounds  (500  —  125),  will  be  23% 
cream.     The  cream  could,  of  course,  be  found  by  forming  the  follow- 
ing simple  proportion. 
11.75     ::     500     :    X 

X  =  375  pounds  of  23%  cream. 

NOTE: — In  the  two  following  exercises  on  Standardization  it  is 
intended  that  one  shall  consist  of  a  problem  where  the  amount  to 
be  standardized  is  definite  and  the  other  shall  be  a  problem  where  the 
resulting  amount  is  indefinite. 


EXERCISE   II 
STANDARDIZING 

1.  Test  for  fat  by  the  Babcock  method  the  samples  of  milk  and 
cream  to  be  used  in  standardization.     Report  the  percentages  of 
fat  found  and  a  definite  percentage  to  which  the  milk  or  cream  is  to 
be  standardized  will  be  assigned. 

2.  After  standardizing  the  milk  or  cream  as  directed,  test  it  for 
fat  by  the  Babcock  method  in  order  to  verify  the  accuracy  of 
work. 


14 

EXERCISE   III 

1.  Test  for  fat  by  the  Babcock  method,  the  samples  of  milk  and 
cream  to  be  used  in  standardization.     Report  the  percentages  of  fat 
found  and  a  definite  percentage  to  which  the  milk  or  cream  is  to  be 
standardized  will  be  assigned. 

2.  After  standardizing  the  milk  or  cream  as  directed,  test  it  for 
fat  by  the  Babcock  method  in  order  to  verify  the  accuracy  of  your 
work. 


STUDENT'S   NOTES  AND   REPORT 


PASTEURIZATION 

Pasteurization  applied  to  dairy  work  is  the  process  of  heating  milk 
or  cream  to  a  temperature  sufficiently  high  and  for  a  time  sufficiently' 
long  to  kill  most  of  the  organisms  in  them.  The  materials  should 
then  be  cooled  to  a  temperature  of  50°  F.  or  lower  to  prevent  germ 
growth.  Cooling  the  product  is  just  as  important  a  part  of  the 
process  as  is  heating,  for  if  there  are  any  organisms  not  killed  by  the 
heating  process,  they  will  multiply  rapidly  if  the  milk  or  cream  is  kept 
at  temperatures  favorable  for  germ  growth.  Milk  or  cream  from 
the  market  standpoint  should  be  kept  at  just  as  low  a  temperature  as 
possible  and  still  not  freeze  them. 

Pasteurization  has  for  its  purpose  two  objects,  (i)  the  killing  of 
pathogenic  organisms,  and  (2)  checking  germ  growth.  The  first  is 
the  most  important,  and  it  is  supposed  that  the  process  of  pasteuriza- 
tion is  efficient  in  destroying  all  pathogenic  organisms.  This  supposi- 
tion is  based  upon  a  great  many  experiments  on  the  thermal  death 
point  of  such  pathogenic  organisms  as  those  which  cause  tuberculosis, 
typhoid,  and  diphtheria. 

Pasteurization  differs  from  sterilization  in  that  the  latter  process 
kills  all  living  material  in  and  about  an  object.  It  is  not  possible  to 
sterilize  milk  for  market  purposes  because  the  high  temperatures  and 
length  of  time  required  for  sterilization  change  the  normal  taste  of 
milk  and  render  it  objectionable  to  the  consumer.  Too  high  tempera- 
tures also  change  the  chemical  composition  of  milk,  the  chief  of  these 
changes  being  the  precipitation  of  albumin  and  causing  the  lime  salts 
to  become  more  insoluble.  For  these  reasons  both  the  degree  of  heat 
and  the  length  of  time  employed  in  the  process  of  pasteurization  are 
limited. 

There  are  two  methods  of  pasteurization  one  called  the  flash 
method  and  the  other  the  holder  method.  In  the  flash  method,  milk 
is  heated  to  a  comparatively  high  temperature  for  a  short  time, 
usually  1 60°  F.  for  one  minute  or  less,  and  frequently  the  time  which 
the  milk  is  subjected  to  the  proper  temperature  is  only  a  few  seconds. 

In  the  holder  method,  milk  is  heated  to  a  low  temperature  for  a 
comparatively  long  period  of  time,  140°  F. — 145°  F.  for  30  minutes 
being  a  very  common  time  and  temperature  employed.  The  holder 
process  of  pasteurization  is  considered  more  efficient  than  the  flash 

16 


17 

method  and  many  boards  of  health  have  forbidden  the  use  of  the  flash 
method  of  pasteurization  of  milk  sold  under  their  jurisdiction. 

Pasteurization  should  never  be  used  as  a  means  of  placing  dirty 
milk  upon  the  market.  While  the  process  does  kill  the  micro- 
organisms found  in  milk  it  does  not  always  destroy  their  products, 
and  if  badly  contaminated  milk  is  pasteurized  and  placed  upon  the 
market,  although  its  germ  content  may  be  small,  it  may  still  be  unfit 
for  human  consumption. 

EXERCISE   IV 
PASTEURIZATION  BY  THE  HOLDER  METHOD 

NOTE: — This  exercise  should  be  performed  in  combination  with 
Exercise  V. 

1 .  Thoroughly  mix  four  cans  of  milk  by  pouring  from  one  can  to 
another.     Take  in  a  sterile  bottle  a  small  amount  of  milk  from  each 
can  and  place  the  sample  on  ice  until  it  can  be  plated  for  bacteria. 
Two  of  the  cans  of  milk  are  to  be  used  in  Exercise  V. 

2 .  Thoroughly  scald  the  machine.     This  may  be  done  by  running 
hot  water  through  the  coils.     Pasteurize  two  cans  of  milk  at  a  tem- 
perature of  140°  F.  for  30  minutes.     After  heating  the  milk  for  the 
proper  time  at  the  proper  temperature,  cool  the  milk  to    as  low  a 
temperature  as  possible  in  the  time  allowed  and  lower  the  temperature 
of  the  milk  as  rapidly  as  possible.     Carefully  record  the  weights  of 
the  milk  used,  the  time  required  to  raise  the  milk  to  140°  F.,  the 
temperature  to  which  the  milk  was  cooled,  the  temperature  of  the 
refrigerating  substance  as  it  enters  the  coils,  and  the  time  required  for 
the  entire  process. 

When  the  process  is  complete,  take  in  a  sterile  bottle  a  sample 
of  the  milk  to  be  plated  for  bacteria.  Compare  the  bacteria  counts 
obtained  with  that  of  the  raw  milk,  and  that  from  the  milk  pas- 
teurized by  the  flash  method. 


i8 
STUDENT'S  NOTES  AND  REPORT 


EXERCISE  V 
PASTEURIZATION  BY  THE  FLASH  METHOD 

NOTE: — This  exercise  should  be  performed  in  combination  with 
Exercise  IV. 

1.  Thoroughly  scald  the  machine.     This  may  best  be  done  by 
allowing  water  to  pass  through  the  machine  and  turning  on  the  steam 
at  the  same  time.    Allow  this  hot  water  to  pass  over  the  cooler  and 
so  far  as  possible  sterilize  it.     Use  for  this  experiment  the  two  cans 
of  milk,  mixed  as  directed  in  Exercise  IV.     Pasteurize  the  milk  at  a 
temperature  of  160°  F.     Carefully  record  the  pounds  of  milk  used, 
time  required  for  the  process,  temperature  of  refrigerating  material 
as  it  enters  and  leaves  the  cooler  and  the  temperature  to  which  the 
milk  is  cooled. 

2.  Take  in  a  sterile  bottle  a  sample  of  the  milk  to  be  plated  for 
bacteria.     Compare  the  count  obtained  with  that  of  the  raw  milk 
and  that  obtained  from  the  milk  pasteurized  by  the  holder  method. 


2O 

STUDENT'S  NOTES  AND  REPORT 


21 

EXPLANATION    OF    EXERCISE   VI 

On  the  average  dairy  farm,  one  of  the  most  practical  methods  of 
cooling  milk  is  to  set  the  can  containing  the  milk  in  a  tank  of  ice  water. 
For  this  purpose  a  cement  tank  is  the  most  durable  and  in  the  long  run 
cheapest.  The  walls  of  the  tank  should  be  from  four  to  six  inches 
thick  and  that  side  on  which  the  milk  is  lifted  in  and  out  of  the  tank 
should  be  faced  with  iron  to  prevent  the  cans  from  chipping  the 
cement.  The  tank  will  be  most  convenient  if  it  is  sunk  in  the  floor 
as  this  will  make  it  easier  to  lift  the  cans  in  and  out.  The  walls 
should,  however,  extend  about  twelve  inches  above  the  floor  to  pre- 
vent dirt  working  into  the  tank.  An  outlet  should  be  made  in  the 
bottom  of  the  tank  so  that  it  may  be  easily  cleaned  as  more  or  less 
milk  will  be  spilled,  causing  the  tank  to  become  unsanitary. 

A  galvanized  iron  tank,  useful  in  cooling  milk  and  capable  of  hold- 
ing four  cans,  may  be  purchased  from  dairy  supply  houses  for  from 
eight  to  ten  dollars. 

In  order  to  have  milk  cool  properly  in  a  tank  of  this  kind  it  is 
necessary  to  frequently  stir  the  milk  in  the  cans.  Unless  milk  is 
stirred  frequently  it  will  not  cool  rapidly  and  rapid  cooling  is  essential 
in  preventing  an  increase  of  germ  life. 

The  purpose  of  the  following  exercise  is  to  show  the  effect  of  stirring 
at  different  intervals  on  the  rapidity  with  which  milk  cools.  The 
student  should  also  draw  conclusions  regarding  the  frequency  with 
which  milk  should  be  stirred  to  get  the  best  practical  results. 

EXERCISE  VI 
COOLING  MILK  IN  CANS 

1.  Heat  four  cans  of  milk  to  95°  F.  and  place  in  a  tank  of  ice 
water.     For  this  experiment  about  135  pounds  of  ice  will  be  required. 

Stir  can  No.  I  every  five  minutes  and  record  the  temperature. 

Stir  can  No.  II  every  ten  minutes  and  record  the  temperature. 

Stir  can  No.  Ill  continuously  and  record  the  temperature  every 
ten  minutes. 

Do  not  stir  can  No.  IV  at  all  but  record  the  temperature  of  the 
milk  in  the  center  at  ten  minute  intervals. 

2.  Carry  on  the  experiment  for  one  hour  and  at  the  end  of  one 
hour  thoroughly  stir  can  No.  IV  and  record  the  temperature  of  the 
mixed  milk  with  that  of  the  temperature  of  the  milk  before  the 
milk  was  thoroughly  stirred. 

3 .  Compare  the  temperature  obtained  in  the  four  different  cans. 
Draw  conclusions  concerning  the  frequency  with  which  milk  should 
be  stirred,  to  get  the  best  practical  results. 


22 

STUDENT'S  NOTES  AND  REPORT 


23 

EXPLANATION   OF  EXERCISE  VII 

There  are  several  kinds  of  conical  coolers  on  the  market,  which  are 
suitable  for  use  on  farms.  These  coolers  furnish  an  efficient  piece 
of  apparatus  at  a  reasonable  price.  Their  use  has  often  been  abused 
since  they  are  frequently  stationed  and  used  in  places  where  they  are 
exposed  to  dust  and  dirt,  and  in  order  to  minimize  the  danger  from 
such  contamination,  some  coolers  are  provided  with  a  hood  which 
surrounds  that  part  of  the  cooler  over  which  the  milk  flows.  The 
refrigerating  material  most  commonly  used  in  these  coolers  is  ice  and 
water,  although  they  may  be  attached  to  a  brine  barrel  or  a  running 
water  supply,  if  such  a  supply  is  available.  Whatever  the  refrigerating 
substance  used  in  these  coolers,  it  should  be  stirred  frequently.  If  it 
is  not  stirred,  the  refrigerating  material  next  to  the  walls  soon  becomes 
warmed  by  the  milk  passing  over  the  cooler  and  so  loses  its  efficiency. 
The  purpose  of  the  following  experiment  is  to  compare  the  effi- 
ciency of  a  conical  type  of  cooler  when  the  refrigerating  material 
inside  the  cooler  is  stirred  and  when  it  is  not  stirred. 

EXERCISE  VII 
COOLING  MILK  WITH  A  CONICAL  COOLER 

1 .  Weigh  a  can  of  whole  milk  and  heat  it  to  95°  F.     The  purpose 
of  heating  the  milk  is  to  bring  it  to  nearly  the  same  temperature  as 
when  drawn  from  the  cow.     Place  forty  pounds  of  ice  inside  the  cooler 
and  fill  the  cooler  to  the  overflow  pipe  with  cold  water.     Run  the 
milk  over  the  cooler  and  note  the  time  it  takes  the  first  milk  which 
comes  from  the  receiving  tank  to  reach  the  outlet  spout  of  the  cooler. 
Do  not  stir  the  water  inside  the  cooler.     Record  the  temperature  of 
the  milk  at  the  outlet  spout  every  three  minutes.     Note  the  time 
required  to  pass  the  milk  over  the  cooler.     After  all  of  the  milk  has 
passed  over  the  cooler,  stir  it  thoroughly  and  record  the  final  tempera- 
ture.    Take  the  temperature  of  the  water  near  the  walls  of  the  cooler. 
Stir  the  water  and  then  take  its  temperature.     Weigh  the  amount  of 
ice  left. 

2 .  Repeat  the  experiment,  heating  the  milk  to  the  same  tempera- 
ture and  using  the  same  amount  of  ice,  but  in  this  case  stir  the  ice 
water  in  the  cooler  continuously.     Record  the  temperature  of  the 
milk  every  three  minutes.     Stir  the  can  of  milk  and  take  the  final 
temperature.     Weigh  the  amount  of  ice  left.     Compare  the  results 
obtained  by  the  two  methods  of  cooling.     Make  a  drawing  of  the 
cooler.     Compute  the  capacity  of  the  cooler  per  hour. 

State  in  your  notes  the  name  of  the  cooler  used. 


24 
STUDENT'S  NOTES  AND   REPORT 


COMPUTING  AMOUNT  OF  ICE  NECESSARY  TO  COOL  A 
GIVEN  AMOUNT  OF   MILK 

The  study  of  refrigeration  is  essentially  a  study  of  heat.  The  unit 
of  heat  used  by  refrigeration  engineers  is  called  the  British  Thermal 
Unit,  and  it  is  the  amount  of  heat  required  to  raise  one  pound  of  water 
one  degree  Fahrenheit  at  its  maximum  density,  39.1°  F. 

Not  all  substances  require  the  same  amount  of  heat  to  raise  their 
temperature  per  unit  of  mass.  Water  is  taken  as  a  standard,  and  the 
ability  of  a  substance  to  absorb  heat  in  comparison  with  water  is 
called  the  specific  heat  of  the  substance.  The  specific  heat  of  water 
is  called  i ,  and  most  substances  have  a  specific  heat  less  than  that  of 
water.  The  specific  heat  of  milk  is  variable,  depending  to  a  large 
extent  upon  the  temperature  and  the  variation  in  fat  content.  The 
lower  the  fat  content  the  higher  the  specific  heat.  The  specific  heat 
of  normal  milk  is  variously  given  by  different  investigators  as  ranging 
between  .92  and  .95.  In  computations  on  refrigeration,  the  melting 
point  of  ice  is  used  as  a  basis,  because  this  is  definite  and  constant.  It 
requires  144  B.  T.  U.  to  melt  one  pound  of  ice,  and  knowing  this  fact, 
the  amount  of  ice  necessary  to  cool  a  given  amount  of  milk  may  be 
readily  computed.  The  method  of  computation  may  best  be  illus- 
trated by  a  specific  problem. 

How  many  pounds  of  ice  will  be  required  to  cool  500  pounds  of 
milk  from  80°  F.  to  32°  F.  ?  In  this  case,  the  specific  heat  of  the  milk 
is  considered  as  .93. 

Five  hundred  X  .93  =  465,  the  number  of  heat  units  required 
to  raise  the  500  pounds  of  milk  one  degree  as  compared  with  the  same 
amount  of  water.  Since  the  milk  is  to  be  cooled  48°  F.  (80  —  32  =48) 
multiplying  465  by  48  will  give  22,320  heat  units  to  be  extracted  from 
the  milk,  (465  X  48  =  22,320).  Since  it  requires  144  B.  T.  U.  to 
melt  one  pound  of  ice,  it  would  require  as  many  pounds  of  ice  to  cool 
the  500  pounds  of  milk  as  144  is  contained  in  22,320,  or  155,  (22,320  -f- 

*44  =   155)- 

If  the  milk  is  cooled  to  a  temperature  above  32°  F.  the  available 
refrigeration  of  one  pound  of  ice  is  increased  and  the  difference 
between  32°  F.  (the  temperature  of  the  melting  ice),  and  the  tempera- 
ture to  which  the  milk  is  cooled,  must  therefore  be  added  to  the 
B.  T.  U.  necessary  to  melt  a  pound  of  ice  (144). 


25 


26 

For  example,  suppose  we  wished  to  find  the  number  of  pounds 
of  ice  necessary  to  cool  500  pounds  of  milk  from  80°  F.  to  40°  F. 
Assuming  the  specific  heat  of  the  milk  to  be  .93,  the  number  of  heat 
units  to  be  extracted  from  the  milk  would  be  500  X  .93  X  40  (80  —  40 
=  40)  =  18,600.  Since  the  milk  is  to  be  cooled  to  a  point  8°  F.  above 
the  melting  point  of  ice  (40  —  32  =  8),  the  available  refrigeration  of  a 
pound  of  ice  would  be  increased  to  152  (144 +  8  =  152).  The  num- 
ber of  pounds  of  ice  necessary  would  therefore  be  1 8 ,600  -f-  152  =  122.3 
pounds. 

The  theoretical  amount  of  ice  will  usually  be  insufficient  to  cool 
milk  to  the  desired  temperature.  This  is  because  of  outside  influences 
such  as  temperature  of  the  air,  temperature  of  the  water  with  which 
the  ice  is  mixed,  and  temperature  of  the  apparatus  through  which  the 
water  is  run. 

EXPLANATION   OF   EXERCISE   VIII 

Lower  temperatures  may  be  obtained  with  a  mixture  of  salt  and 
ice  than  with  ice  alone.  This  is  because  of  the  fact  that  when  two 
solids  unite  to  form  a  liquid,  they  absorb  heat.  Within  certain  limits 
the  larger  the  percentage  of  salt  used,  the  lower  the  temperature  that 
can  be  obtained.  After  a  certain  amount  of  salt  has  been  added  the 
solution  becomes  saturated  and  the  further  addition  of  salt  has  no 
effect  in  lowering  the  temperature. 

The  following  table  from  B.  A.  I.  Bulletin  No.  98  gives  the  approxi- 
mate temperatures  which  may  be  obtained  with  different  percentages 
of  salt  and  ice. 

Percentage  of  salt  in  Temperature  of  %  of  salt  in  Temperature  of  salt 

mixture  mixture  mixture  m  mixture 

op  op 

o  32  15  ii 

5  27  20  1.5 

10  20  25  -IO 


27 

EXERCISE  VIII 
COMPARATIVE  EFFICIENCY  OF  ICE  WATER  AND  BRINE  AND  ICE 

Use  for  this  experiment  a  Tubular  cooler. 

Heat  two  cans  of  milk  to  Q5°F.  The  purpose  of  heating  the  milk 
to  this  temperature  is  to  have  it  nearly  the  same  temperature  as  when 
drawn  from  the  cow.  Weigh  the  amount  of  milk  used.  Weigh  out 
about  125  pounds  of  ice.  Crush  it  and  place  it  in  the  brine  barrel. 
Run  in  cold  water  until  the  barrel  is  about  half  full.  Stir  the  mixture 
of  ice  and  water.  Allow  the  pump  to  run  for  about  two  minutes  or 
until  the  temperature  of  the  water  in  the  barrel  is  32°  F.  before  run- 
ning the  milk  over  the  cooler.  Then  run  the  milk  over  the  cooler  at 
its  full  capacity.  Record  the  length  of  time  required  to  cool  the  milk 
and  take  the  temperature  of  the  milk  at  the  outlet  faucet  every  three 
minutes.  Thoroughly  stir  the  milk  in  the  can  and  record  the  final 
temperature.  Record  the  temperature  of  the  return  water  from  the 
cooler  every  three  minutes.  Weigh  the  amount  of  ice  left. 

Repeat  the  experiment,  heating  the  milk  to  95°  F.  and  using  the 
same  amount  of  ice.  The  ice  left  from  the  previous  experiment 
may  be  used  in  this  one.  Add  40  pounds  of  salt  to  the  mixture  in  this 
barrel  and  thoroughly  stir  until  the  salt  is  dissolved.  The  amount 
of  salt  required  will  depend  somewhat  on  its  quality.  If  it  is  insoluble, 
more  will  be  required.  Have  the  temperature  at  28°  F.  to  30°  F. 
Take  temperature  of  the  milk  every  three  minutes,  the  temperature 
of  the  return  water  every  three  minutes,  and  the  final  temperature  of 
the  milk  in  the  can.  Weigh  the  amount  of  ice  left.  Draw  diagram 
of  the  cooler,  and  figure  out  its  capacity  per  hour.  Show  in  drawing 
the  relative  position  of  the  cooler,  brine  barrel,  and  pump. 


28 

STUDENT'S   NOTES  AND   REPORT 


Heat  to  a  temperature  of  95°  P.,  two  cans  of  milk.  Weigh  out 
125  pounds  of  ice,  crush  it,  and  place  it  in  the  brine  barrel  which  has 
previously  been  filled  about  half  full  of  cold  water.  Add,  in  salt,  to 
the  ice  water  in  the  barrel,  5%  of  the  weight  of  the  ice.  Thoroughly 
mix  the  salt  and  ice  water  in  the  barrel  and  pump  the  brine  through 
the  cooler,  noting  its  temperature  before  starting  to  cool  the  milk. 

Cool  the  milk  and  take  the  temperature  of  the  mixed  milk  after 
cooling.  Also  take  the  temperature  of  the  brine  as  it  comes  from  the 
cooler.  Weigh  the  ice  if  any  is  left,  and  save  it  for  use  in  the  second 
part  of  the  experiment. 

Remove  all  of  the  brine  from  the  barrel  and  flush  out  the  barrel 
and  cooler  by  pumping  cold  water  through  them.  Repeat  the  above 
experiment  using  1 5%  of  salt  instead  of  5%.  Record  all  temperatures 
the  same  as  in  the  first  part  of  the  experiment. 


30 
STUDENT'S  NOTES  AND   REPORT 


THE  DAIRY  SCORE  CARD 

The  dairy  score  card  is  a  card  on  which  are  enumerated  the  good 
points  which  a  dairy  should  possess,  and  these  points  are  given 
numerical  values.  The  score  card  is  divided  into  two  distinct 
divisions,  equipment  and  method.  Out  of  a  possible  100  points  for  a 
perfect  score,  40  are  given  to  equipment  and  60  to  methods.  This 
numerical  division  is  made  to  give  a  just  recognition  to  the  importance 
of  proper  methods  in  the  production  of  clean  milk.  Good  equipment 
should  be  an  aid  in  clean  milk  production,  and  other  things  being 
equal,  a  dairyman  will  produce  better  milk  with  good  equipment  than 
with  poor  equipment.  However,  good  equipment  without  proper 
method  will  not  produce  wholesome  milk. 

Those  who  use  the  score  card  should  not  regard  it  as  an  infallible 
set  of  rules  from  which  no  deviation  should  ever  be  made.  It  is 
simply  a  guide  to  help  the  producer  to  see  the  conditions  of  his  dairy 
and  to  help  the  inspector  to  judge  intelligently  of  those  conditions. 

The  chief  value  of  the  score  card  is  that  when  properly  used  it  is 
educational,  and  it  is  educational  because  it  not  only  points  out 
defects,  but  it  emphasizes  the  seriousness  of  these  defects.  In  this 
way  the  dairyman  is  given  a  chance  to  improve  in  these  things  which 
will  aid  most  in  clean  milk  production. 


32 

EXPLANATION  OF  EXERCISES  X,  XI  AND  XII 

Score  dairies  according  to  the  official  score  card,  and  place  the 
score  of  the  different  points  on  the  card.  In  the  blank  page  reserved 
for  notes,  write  a  short  criticism  of  the  place  scored,  and  note  those 
things  which  might  be  done  to  improve  the  milk  supply,  and  at  the 
same  time  would  not  require  a  big  outlay  of  capital.  Also  criticise 
the  methods  employed,  in  the  same  way. 

NOTE  : — It  is  intended  that  at  least  three  dairies  of  different  grade 
should  be  scored,  one  having  excellent  buildings  and  equipment,  one 
having  medium  buildings  and  equipment,  and  one  having  poor 
buildings  and  equipment.  It  would  be  desirable  if  the  high  grade 
dairy  was  producing  certified  milk,  or  milk  of  similar  grade,  and  the 
poorly  equipped  dairy  was  producing  a  good  grade  of  milk  by  means  of 
superior  methods.  This  would  emphasize  the  importance  of  clean 
milk  production.  If  time  permits,  more  than  three  dairies  may  be 
scored,  as  it  is  highly  desirable  that  all  the  practice  possible  be  given 
to  this  part  of  clean  milk  production. 

EXERCISE  X 
JUDGING  DAIRY  BARNS 

1.  Score  according  to  the  official  score  card  the  dairy  visited. 
Place  the  score  allowed  the  different  points  on  the  score  card. 

2.  On  the  sheet  allotted  to  notes,  write  a  brief  criticism  of  the 
dairy  and  the  methods  employed.     Pay  particular  attention  to  those 
things  which  are  important  in  clean  milk  production,  and  at  the  same 
time  would  not  require  a  big  outlay  of  capital. 


STUDENT'S  NOTES  AND  REPORT 

SCORE 


EQUIPMENT 

SCORE 

METHODS 

SCORE 

Perfect 

Allowed 

Perfect 

Allowed 

cows 

6 

cows 
Clean  

8 
6 

5 

I 

Apparently  in  good  health       ....      I 

Free  from  visible  dirt  6 

STABLE 

If  tested  with  tuberculin  within  a 
year  and  no  tuberculosis  is  found, 
or  if  tested  within  six  months  and 
all  reacting  animals  removed  .  .  .  .  5 
If  tested  within  a  year  and  reacting 
animals  are  found  and  removed  3 

Floor                         ...          2 

Walls                        r 

Water,  clean  and  fresh  

i 

Mangers  and  partitions  i 

STABLES 

Location  of  stable  

3 

Freedom  from  odors  2 

Well  drained  I 

4 

4 

i 
7 

I 
I 

5 

i 

Cleanliness  of  bedding  

Free  from  contaminating  surround- 
ings                                       i 

Barnyard  

2 

Clean  .  .                             i 

2 

Tight,  sound  floor  and  proper  gutter2 
Smooth,  tight  walls  and  ceiling.  .  .  .  i 
Proper  stall,  tie,  and  manger  i 
Provision   for  light:     Four   sq.   ft.    of 
glass  per  cow 

Removal  of  manure  daily  

To  50  feet  or  more  from  stable. 

MILK   ROOM   OR   MILK    HOUSE 

Cleanliness  of  milk  room  

3 

8 

9 

Three  sq.  ft.,  3;   2  sq.  ft.,  2;    i  sq.  ft'. 
i.     Deduct  for  uneven  distribution. 

Ventilation    

UTENSILS    AND    MILKING 

Care  and  cleanliness  of  utensils  
Thoroughly  washed  2 



Provision  for  fresh  air,  controllable 
flue  system  3 

Windows   hinged   at   bottom,    1.50: 
sliding  windows  i  ;   other  openings  .50. 
Cubic  feet  of  space  per  cow,  500  feet3 
Less  than  500  ft.  ,  2  ;  less  than  400  ft.  , 
i;    less  than  300  ft.,  o. 
Provision    for   controlling    tempera- 
ture                                     i 

Sterilized  in  steam  for  15  minutes.  .  .  .3 
Placed  over  steam  jet  or  scalded  with 
boiling  water,  2. 
Protected  from  contamination  3 
Cleanliness  of  milking  

UTENSILS 

Construction  and  condition  of  utensils 
Water  for  cleaning 

Clean,  dry  hands  3 

Udders  washed  and  wiped  6 

Udders  cleaned  with  moist  cloth,  4  ; 
cleaned  with  dry  cloth  or  brush  at  least 
15  minutes  before  milking,  i. 

HANDLING   THE   MILK 

Cleanliness  of  attendants  in  milk  room 
Milk  removed  immediately  from  stable 
without  pouring  from  pail    .    ... 

Clean,  convenient  and  abundant. 
Small-top  milking  pail 

Milk  cooler  

Clean  milkinp  suits.  . 

i 

MILK    ROOM.  OR   MILK   HOUSE 

Location  free  from  contaminating  sur- 
roundings   

i 

2 

Cooled  immediately  after  milking  each 

Cooled  below  50°  F 

5 
3 

2 

Si°  to  5S°,  4;  56°  to  60°,  2. 

Construction  of  milk  room  . 

51°  to  55°,  2;    56°  to  60°,  i. 
Transportation  below  50°  F  

Floor,  walls  and  ceiling  i 

I 
I 

Separate   rooms   for   washing    utensils 
and  handling  milk  

Si°  to  55°,  i-So;    56°  to  60°  I. 

If  delivered  twice  a  day  allow  perfect 
score  for  storage  and  transportation. 

Total    

Facilities  for  steam  Hot  water  0.5.  ... 
Total    

40 

60 

Equipment. 


+  Methods = Final  Score. 


NOTE  i — If  any  exceptionally  filthy  condition  is  found,  particularly  dirty  utensils,  the  total  score  may  be 
further  limited. 

NOTTS  2 — If  the  water  is  exposed  to  dangerous  contamination,  or  there  is  evidence  of  the  presence  of  a  dan- 
gerous disease  in  animals  or  attendants,  the  score  shall  be  o. 


SANITARY  INSPECTION  OF  DAIRY  FARMS 


MARKET   MILK    PRODUCTION 


SCORE    CARD 

* 

Indorsed  by  the  Official  Dairy  Instructors'  Association. 

Owner  or  lessee  of  farm : 

P.  O.  address .State 

Total  number  of  cows Number  milking 

(jallonsof  milk  produced  daily 

Product  is  sold  by  producer  to  families,  hotels,  restaurants,  stores, 

•v 

to dealer 

For  milk  supply  of 

Permit  No Date  of  inspection 191 .. 

REMARKS.  . 


(Signed) 

Inspector 

43 


35 

EXERCISE  XI 
JUDGING  DAIRY  BARNS 

1.  Score  according  to  the  official  score  card,'  the  dairy  visited. 
Place  the  score  allowed  the  different  points,  on  the  score  card. 

2.  On  the  sheet  allotted  to  notes,  write  a  brief  criticism  of  the 
dairy  and  the  methods  employed.     Pay  particular  attention  to  those 
things  which  are  important  in  clean  milk  production,  and  at  the  same 
time  would  not  require  a  big  outlay  of  capital . 


STUDENT'S  NOTES  AND  REPORT 

SCORE 


EQUIPMENT 

SCORE 

METHODS 

SCORE 

Perfect 

Allowed 

Perfect 

Allowed 

cows 

Hoaltti 

6 

i 

cows 
Clean  

8 
6 

S 

i 

Free  from  visible  dirt  6 

STABLE 

Cleanliness  of  stable  

If  tested   with   tuberculin  within  a 
year  and  no  tuberculosis  is  found, 
or  if  tested  within  six  months  and 
all  reacting  animals  removed  .  .  .  .  5 
If  tested  within  a  year  and  reacting 
animals  are  found  and  removed  3 
Food  clean  and  wholesome      

Floor  2 

Walls   i 

Ceiling  and  ledges  i 

Water,  clean  and  fresh  

i 

Mangers  and  partitions  i 

STABLES 

Location  of  stable  

2 

Windows  i 

Stable  air  at  milking  time  

Freedom  from  dust  3 

Freedom  from  odors  2 

Well  drained                                           i 

4 

4 

I 
7 

i 

i 

S 
I 

Cleanliness  of  bedding  

Free  from  contaminating  surround- 
ings                             i 

Barnyard  

2 

Construction  of  stable 

2 

Tight,  sound  floor  and  proper  gutter2 
Smooth,  tight  walls  and  ceiling.  .  .  .  i 
Proper  stall,  tie,  and  manger  i 
Provision   for   light:     Four   sq.   ft.    of 
glass  per  cow   

Wei!  drained  i 

Removal  of  manure  daily  

MILK   ROOM   OR   MILK   HOUSE 

Cleanliness  of  milk  room  

3 

8 
9 

2 

Three  sq.  ft.,  3;    2  sq.  ft.,  2;    I  sq.  ft., 
i.     Deduct  for  uneven  distribution. 

Ventilation    

UTENSILS    AND    MILKING 

Care  and  cleanliness  of  utensils  
Thoroughly  washed  2 

Provision  for  fresh  air,  controllable 
flue  system  .                                          •; 

Windows   hinged    at    bottom,    1.50 
sliding  windows  i  ;   other  openings  .50. 
Cubic  feet  of  space  per  cow,  500  feet3 
Less  than  500  ft.,  2;  less  than  400  ft., 
i;    less  than  300  ft.,  o. 
Provision    for    controlling    tempera- 
ture .      .                                             i 

Sterilized  in  steam  for  15  minutes  ...  .3 
Placed  over  steam  jet  or  scalded  with 
boiling  water,  2. 
Protected  from  contamination  3 

UTENSILS 

Construction  and  condition  of  utensils 
Water  for  cleaning  

Clean,  dry  hands  •? 

Udders  washed  and  wiped  6 
Udders  cleaned  with  moist  cloth,  4; 
cleaned  with  dry  cloth  or  brush  at  least 
15  minutes  before  milking,  i. 

HANDLING    THE    MILK 

Cleanliness  of  attendants  in  milk  room 

Clean,  convenient  and  abundant. 
Small-top  milking  pail 

M  ilk  cooler  

Clean  milkinp  suits  

I 

Milk  removed  immediately  from  stable 

MILK    ROOM.  OR    MILK    HOUSE 

Location  free  from  contaminating  sur- 
roundings   

I 

2 

Cooled  immediately  after  milking  each 

2 

5 
3 

2 

Cooled  below  50°  F  

51°  to  55°,  4;  56°  to  60°,  2. 

Construction  of  milk  room 

51°  to  55°,  2;   56°  to  60°,  i. 
Transportation  below  50°  F  

Floor,  walls  and  ceiling  i 

I 
I 

Separate   rooms   for   washing   utensils 
and  handling  milk  

51°  to  55°,  1.50;    56°  to  60°  i. 

If  delivered  twice  a  day  allow  perfect 
score  for  storage  and  transportation. 

Total    

Facilities  for  steam  Hot  water  0.5  .... 
Total    

40 

60 

Equipment.. 


-f-  Methods = Final  Score.. 


NOTE  i — If  any  exceptionally  filthy  condition  is  found,  particularly  dirty  utensils,  the  total  score  may  be 
further  limited. 

NOTE  * — If  the  water  is  exposed  to  dangerous  contamination,  or  there  is  evidence  of  the  presence  of  a  dan- 
gerous disease  in  animals  or  attendants,  the  score  shall  be  o. 


SANITARY  INSPECTION  OF  DAIRY  FARMS 


MARKET  MILK  PRODUCTION 


SCORE    CARD 

Indorsed  by  the  Official  Dairy  Instructors'  Association. 

Owner  or  lessee  of  farm 

P.  O.  address State 

Total  number  of  cows Number  milking 

Gallons  of  milk  produced  daily 

Product  is  sold  by  producer  to  families,  hotels,  restaurants,  stores, 

to dealer 

For  milk  supply  of. 

Permit  No.. Date  of  inspection 191 .  . 

REMARKS.  . 


(Signed) 

Inspector 


38 

EXERCISE   XII 
JUDGING  DAIRY  BARNS 

1.  Score  according  to  the  official  score  card,  the  dairy  visited. 
Place  the  score  allowed  the  different  points,  on  the  score  card. 

2.  On  the  sheet  allotted  to  notes,  write  a  brief  criticism  of  the 
dairy  and  the  methods  employed.     Pay  particular  attention  to  those 
things  which  are  important  in  clean  milk  production,  and  at  the  same 
time  would  not  require  a  big  outlay  of  capital. 


STUDENT'S  NOTES  AND  REPORT 

SCORE 


EQUIPMENT 

SCORE 

METHODS 

SCORE 

Perfect  Allowed 

Perfect 

Allowed 

cows 
Health  

6 

i 

cows 
Clean                                       

8 
6 

5 

i 

Apparently  in  good  health       .            I 

STABLE 

Clsanliness  of  stable  

If  tested  with  tuberculin  within  a 
year  and  no  tuberculosis  is  found, 
or  if  tested  within  six  months  and 
all  reacting  animals  removed  ....  5 
If  tested  within  a  year  and  reacting 
animals  are  found  and  removed  3 
Food  clean  and  wholesome 

Floor  2 

Walls   i 

Ceiling  and  ledges  i 

Water,  clean  and  fresh 

i 

Mangers  and  partitions  i 
Windows  i 

STABLES 

Location  of  stable 

2 

Stable  air  at  milking  time    

Freedom  from  odors  2 

Well  drained  I 

4 

4 

I 

7 

I 
I 

Cleanliness  of  bedding  

Free  from  contaminating  surround- 
ings .                                                    i 

Barnyard  

2 

Construction  of  stable 

Clean  i 

- 

Tight,  sound  floor  and  proper  gutter: 
Smooth,  tight  walls  and  ceiling.  .  .  .  ) 
Proper  stall,  tie,  and  manger  ] 
Provision  for  light:     Four   sq.   ft.    o! 
glass  per  cow   

Well  drained  .  .        i 

To  50  feet  or  more  from  stable. 

MILK   ROOM   OR   MILK   HOUSE 

Cleanliness  of  milk  room  

3 

8 

9 

2 

Three  sq.  ft..  3;    2  sq.  ft.,  2;    I  sq.  ft. 
I.     Deduct  for  uneven  distribution. 

Ventilation 

UTENSILS   AND   MILKING 

Care  and  cleanliness  of  utensils  
Thoroughly  washed  2 

Provision  for  fresh  air,  controllabl. 
flue  system  .  . 

Windows   hinged   at   bottom,    1.50 
sliding  windows  i;   other  openings  .50 
Cubic  feet  of  space  per  cow,  500  feet. 
Less  than  500  ft.  ,  2  ;   less  than  400  ft.  . 
i;    less  than  300  ft.,  o. 
Provision   for   controlling    tempera- 
ture                             i 

Sterilized  in  steam  for  15  minutes.  .  .  .3 
Placed  over  steam  jet  or  scalded  with 
boiling  water,  2. 
?rotected  from  contamination  3 
Cleanliness  of  milking  

UTENSILS 

Construction  and  condition  of  utensils 
Water  for  cleaning  

Udders  washed  and  wiped  6 

Udders  cleaned  with  moist  cloth,  4  ; 
:leaned  with  dry  cloth  or  brush  at  least 
15  minutes  before  milking,  i. 

HANDLING    THE   MILK 

Cleanliness  of  attendants  in  milk  room 
Milk  removed  immediately  from  stable 

Clean,  convenient  and  abundant. 
Small-top  milking  pail 

5 

i 

M  ilk  cooler  

Clean  milking  suits  

i 
i 

2 

MILK    ROOM.  OR    MILK    HOUSE 

Location  free  from  contaminating  sur- 
roundings   

Cooled  immediately  after  milking  each 

2 

s 

3 

2 

Cooled  below  50°  F   .    . 

51°  to  55°,  4;  56°  to  60°,  2. 

Construction  of  milk  room 

Si°  to  55°,  2;    56°  to  60°,  i. 
Transportation  below  <;o0  F  

Floor,  walls  and  ceiling  ".  .  i 

I 
I 

Separate  rooms  for  washing   utensils 
and  handling  milk  

51°  to  55°,  i-So;    56°  to  60°  i. 

If  delivered  twice  a  day  allow  perfect 
score  for  storage  and  transportation. 

Total                   .... 

• 

Facilities  for  steam  Hot  water  0.5  .... 
Total    .  . 

40 

60 

Equipment.. 


+  Methods = Final  Score. 


NOTE  i — If  any  exceptionally  filthy  condition  is  found,  particularly  dirty  utensils,  the  total  score  may  be 
further  limited. 

NOTE  2 — If  the  water  is  exposed  to  dangerous  contamination,  or  there  is  evidence  of  the  presence  of  a  dan- 
gerous disease  in  animals  or  attendants,  the  score  shall  be  o. 


SANITARY  INSPECTION  OF  DAIRY  FARMS 


MARKET  MILK  PRODUCTION 


SCORE    CARD 

Indorsed  by  the  Official  Dairy  Instructors'  Association. 

Owner  or  lessee  of  farm - 

P.  O.  address State 

Total  number  of  cows Number  milking 

Gallons  of  milk  produced  daily 

Product  is  sold  by  producer  to  families,  hotels,  restaurants,  stores, 

to dealer 

For  milk  supply  of 

Permit  No Date  of  inspection 191 . . 

REMARKS.  . 


(Sinned) 

Inspector 


41 

EXERCISE  XIII 
JUDGING  CITY  MILK  PLANT 

1.  Judge  according  to  the  official  score  card,  a  city  milk  plant. 
Place  the  scores  allowed  on  the  card. 

2.  On  the  sheet  allotted  to  notes,  write  a  brief  criticism  of  the 
plant  and  the  methods  employed.     Note  especially  the  arrangement 
of  the  plant  as  regards  convenience  for  performing  work.     Also  note 
the  location  and  condition  of  the  plant  in  regard  to  its  sanitary  sur- 
roundings.    Point  out  any  improvements  either  in  equipment  or 
methods  which  would  be  beneficial  and  at  the  same  time  require  only 
a  small  outlay  of  capital. 


STUDENT'S  NOTES  AND  REPORT 
SANITARY  INSPECTION  OF  CITY  MILK  PLANTS 


Owner  or  manager  ..........................................  Trade  name  . 

City  ....................  Street  and  No  ........................  State  .  .  . 

f  Milk  .....  .  ....... 

Number  of  wagons  ..................  Gallons  sold  daily  < 


Cream 


Permit  or  License  No Date  of  inspection ,  191 


EQUIPMENT 

SCORE 

METHODS 

SCORE 

Perfeit 

Allowed 

Perfect 

Allowed 

BUILDING: 
Location:     Free  from  contaminating 

2 

BUILDING                            

15 

Cleanliness: 
Floors                                                .  3 

16 
16 

9 

4 

6 
8 

20 

Walls                                             .  .    i 

Shafting,  pulleys,  hangers,  pipes,  i 

Freedom  from  flies  and  other  insects  3 
Drainage      2 

Construction  

Floors  tight,  sound,  cleanable  t 
Walls  tight,  smooth,  cleanable  .  .  .  .  i 
Ceilings  smooth,  tight,  cleanable.  .  i 
Provision  for  light  i 

APPARATUS 

Cleanliness: 
Thoroughly  washed  and  rinsed  .  .  6 
Sterilized    in   live   steam,    thirty 
minutes    .          5 

Provision  for  pure  air  I 

(Thoroughly     scaled     after 
washing  with  water  over 
200°  F.  or  live  steam,  3.) 

Minimum  of  shafting,  pulleys,  hang- 
ers, exposed  pipes,  etc  i 

APPARATUS   .  '.  

Boiler  2 

2 

Hot-  water  heater  i 

HANDLING  MILK  

Received  below   "50°  F  5 

Appliances  for  cleansing  utensils  anc 

(50°-55°,  4:  55°-6o°,  3.) 
Rapidity  of  handling  in  plant  3 

Racks,  etc.,  for  utensils  and  bottles 

Freedom  from  undue  exposure  to  air 
in  the  plant  2 

Sterilizer  for  utensils  and  bottles  .  .  2 
Bottling  and  capping  machine  i 
Wash    bowl,    soap,    and   towel   for 

Capping  bottles  by  machine.            i 

Bottle  top   and   cap   protected   by 
covering  2 

RtoraTe  45°  F.  or  below  3 

Protection  during  delivery  2 

(45°-SO°,    2;     50°-S5°.    i.) 
INSPECTION 

Condition  of  apparatus  (make  deduc- 
tion for  inaccessible  parts,  open 
seams,    rusty    ware,    decayed    or 
battered    tables    or    sink,    milk- 
carrying  pipes  with  rough  interiois 
and  lack  of  frequent  hand  coup- 
lings, and  for  badly  worn  and 
poorly  repaired  material)  4 
LABORATORY  AND  EQUIPMENT  

Inspection  of  dairies  supplying  milk  5 
(Once  a  year,  i  ;    twice  a  year,  2  ; 
three  times  a  year,  3;    four 
times  a  year,  4.) 

MISCELLANEOUS  ... 

Cleanliness  of  attendants  2 

Clean,  fresh  i 

(General  appearance,  hands,  etc., 
i  ;  clean,  washable  clothing,  i.) 

Convenient  and  abundant  i 

Total    

Total 

40 

00 

Score  for  equipment plus  score  for  methods equals  TOTAL  SCORE 

NOTE — If  the  conditions  in  any  particular  are  so  exceptionally  bad  as  to  be  inadequately  expressed  by  a 
score  of  "o"  the  inspector  can  make  a  deduction  from  the  tct  il  score. 

,  Inspector. 


43 

EXERCISE  XIV 
JUDGING  CITY  MILK  PLANT 

1.  Judge  according  to  the  official  score  card,  a  city  milk  plant. 
Place  the  scores  allowed  on  the  card. 

2.  On  the  sheet  allotted  to  notes,  write  a  brief  criticism  of  the 
plant  and  the  methods  employed.     Note  especially  the  arrangement 
of  the  plant  as  regards  conveniences  for  performing  work.     Also  note 
the  location  and  condition  of  the  plant  in  regard  to  its  sanitary  sur- 
roundings.    Point  out  any  improvements  either  in  equipment  or 
methods  which  would  be  beneficial  and  at  the  same  time  require  only 
a  small  outlay  of  capital. 


STUDENT'S  NOTES  AND  REPORT 
SANITARY  INSPECTION  OF  CITY  MILK  PLANTS 


Owner  or  manager Trade  name . 

City Street  and  No State  .  .  . 

f  Milk 

Number  of  wagons Gallons  sold  daily  < 

[  Cream 


Permit  or  License  No Date  of  inspection ,191 


EQUIPMENT 

SCORE 

METHODS 

SCORE 

Perfect 

Allowed 

Perfect 

Allowed 

BUILDING: 

Location:     Free  from  contaminating 
surroundings  

2 

BUILDING  

15 

Cleanliness: 
Floors  .3 

16 

• 

16 

9 

4 

Arrangement  

6 

8 

Walls   .             i 

Separate  receiving  room  i 
Separate  handling  room  2 

Ceilings    ...                       .        .  2 

Shafting,  pulleys,  hangers,  pipes,  i 

Freedom  from  flies  and  other  insects  3 
Drainage                                                 2 

Construction  

Floors  tight,  sound,  cleanable  i 
Walls  tight,  smooth,  cleanable  .  .  .  .  i 
Ceilings  smooth,  tight,  cleanable  .  .  I 

APPARATUS 

Cleanliness: 
Thoroughly  washed  and  rinsed.  .6 
Sterilized    in   live   steam,   thirty 
minutes    5 



Minimum  of  shafting,  pulleys,  hang- 

(Thoroughly    scaled     after 
washing  with  water  over 
200°  F.  or  live  steam,  3.) 

APPARATUS   :  

Boiler  2 

2 

HANDLING  MILK  

Received  below  50°  F  5 

Appliances  for  cleansing  utensils  and 

(50°-55°,  4;  SS°-6o°,  3.) 
Rapidity  of  handling  in  plant  3 

Racks,  etc.,  for  utensils  and  bottles 

Freedom  from  undue  exposure  to  air 
in  the  plant  2 

Sterilizer  for  utensils  and  bottles  .  .  2 
Bottling  and  capping  machine  i 

Capping  bottles  by  machine              i 

Bottle   top  and   cap  protected   by 
covering  2 

Wash    bowl,    soap,    and    towel   for 

Storage  45°  F.  or  below  3 

Protection  during  delivery  2 

(4S°-50°,    2;     SO°-SS°,    i.) 
INSPECTION  

Condition  of  apparatus  (make  deduc- 
tion for  inaccessible  parts,  open 
seams,    rusty    ware,    decayed    or 
battered    tables    or    sink,    milk- 
carrying  pipes  with  rough  interiors 
and  lack  of  frequent  hand  coup- 
lings, and  for  badly  worn  and 
poorly  repaired  material)  4 
LABORATORY  AND  EQUIPMENT  

Bacteriological  work  4 

Inspection  of  dairies  supplying  milk  5 
(Once  a  year,  i  ;    twice  a  year,  2  ; 
three  times  a  year,  3;    four 
times  a  year,  -  4.) 

M  ISCELLANEOUS   

Cleanliness  of  attendants  2 

WATER  SUPPLY 

2 

Clean,  fresh  i 

(General  appearance,  hands,  etc., 
i;  clean,  washable  clothing,  i.) 
Cleanliness  of  delivery  outfit              2 

Convenient  and  abundant  i 

Total    

Total 

40 



60 

Score  for  equipment plus  score  for  methods equals  TOTAL  SCORE 

NOTE — If  the  conditions  in  any  particular  are  so  exceptionally  bad  as  to  be  inadequately  expressed  by  a 
score  of  "o"  the  inspector  can  make  a  deduction  from  the  total  score. 

,  Inspector. 


45 

EXPLANATION    OF    EXERCISES    XV   AND    XVI 

The  ability  to  judge  the  flavor  and  odor  of  milk  and  cream  requires 
considerable  practice.  There  are  people  whose  sense  of  taste  and 
smell  is  not  sufficiently  acute  to  enable  them  to  become  good  milk  and 
cream  judges.  Persons  who  have  these  two  senses  developed  to  at 
least  a  normal  degree  can,  by  practice,  become  very  proficient  in 
detecting  odors  and  flavors  in  dairy  products. 

The  first  thing  to  note  in  judging  milk  or  cream  is  the  visible  dirt. 
The  sediment  found  in  milk  is  usually  heavier  than  the  other  contents 
of  the  bottle,  and  therefore  sinks  to  the  bottom  of  the  package.  The 
dirt  is  detected  by  raising  the  bottle  above  the  eye  and  noting  the 
sediment  resting  on  the  bottom.  In  order  to  judge  milk  or  cream 
properly,  the  container  should  be  left  undisturbed  for  at  least  an  hour, 
to  give  sediment  plenty  of  time  to  settle.  In  raising  the  bottle  above 
the  eye,  great  care  should  be  taken  not  to  agitate  the  contents  and  so 
drive  the  dirt  into  suspension.  A  reading  glass  or  hand  lens  is  useful 
in  aiding  one  to  detect  sediment  in  a  bottle  of  milk  or  cream. 

The  package  and  seal  should  be  judged  before  the  latter  is  dis- 
turbed, and  before  breaking  the  seal  the  contents  of  the  bottle  should 
be  well  shaken  so  that  the  milk  or  cream  will  be  thoroughly  mixed  for 
bacteriological  and  chemical  analysis.  Bacteriological  examination 
should  be  made  as  soon  as  the  package  is  opened  before  the  milk  or 
cream  becomes  contaminated  in  any  way.  In  milk  and  cream  con- 
tests, several  bottles  of  the  same  lot  of  milk  are  entered  and  one  of 
these  is  reserved  for  bacteriological  analysis. 

After  judging  the  package  for  appearance,  the  sample  is  next 
examined  for  flavor  and  odor.  In  judging  for  flavor  and  odor  it 
is  best  to  warm  the  sample  slightly,  as  a  low  temperature  disguises 
odors  and  flavors  in  milk  or  cream. 

In  order  to  keep  the  sense  of  taste  acute  it  is  necessary  to  rinse  out 
the  mouth  with  warm  water  after  tasting  each  sample. 


46 

EXERCISE  XV' 
JUDGING  MILK 

i .  Judge  according  to  the  official  score  card,  the  samples  of  milk 
furnished.  If  enough  score  cards  are  not  available,  the  page  allotted 
to  notes  mlay  be  ruled  off  and  used  to  record  the  scores  of  the  different 
samples.  Before  beginning  the  work  of  this  exercise,  read  carefully 
the  directions  on  the  back  of  the  score  card  and  those  on  page 

NOTE  : — Plating  milk  for  bacteria  involves  considerable  time  and 
labor.  If  it  is  impossible  to  plate  the  samples  judged,  the  bacteria 
score  may  be  called  perfect,  and  the  milk  judged  according  to  the 
other  points  on  the  card.  This  will  not  give  the  true  quality  of  the 
milk,  but  it  will  give  the  student  practice  in  methods  of  judging  which 
is  the  prime  purpose  of  this  exercise.  This  is  particularly  true  in 
regard  to  detecting  flavors  and  odors. 


DEPARTMENT  OF  DAIRY  INDUSTRY 


SCORE  CARD  FOR  MILK 


Place 


Exhibit  No . 


Exhibitor 


Address. 


Date, 


ITEM 

PERFECT 
SCORE 

SCORE 
ALLOWED 

REMARKS 

Bacteria  found  per  \  

Flavor  and  odor    .  .  . 

35 
25 

10 
10 

10 

5 

c 

cubic  centimeter  J 
(  Flavor   

(  Odor  

V  isible  dirt    
Pit 

Per  cent  found    

Per  cent  found    

Per  cent  found  

Bottle  and  cap 

j  Cap  

Total    

IOO 

(  Bottle  

(Signed) . 

...191 

47 


Judge 


DIRECTIONS  FOR  SCORING 


BACTERIA  PER  CUBIC  CENTIMETER— PERFECT  SCORE,  35 


POINTS 

Less  than  400 35 

400  to  700 34.5 

700  to  i  ,000 34 

1,000  to  2,000 33.5 

2,000  to  3,000 33 

3,000  to  4,000 32.5 

4,000  to  5,000 32 

5,000  to  6,000 31.5 

6,000  to  7,000 31 

7,000  to  8,000 30.5 

8,000  to  9,000 30 

9,000  to  10,000 29 

10,000  to  15,000 28 

15,000  to  20,000 27 

20,000  to  25,000 26 

25,000  to  30,000 25 

30,000  to  35,000 24 

35,000  to  40,000 23 

40,OOO  tO  45.OOO 22 

45,000  to  50,000. 


POINTS 

55,000  to  60,000 i9- 
60,ooo  to  65,000 18 

65,000  to  70,000 17 

70,000  to  75,000 16 

75,000  to  80,000 15 

80,000  to  85,000 14 

85,000  to  90,000 13 

90,000  to  95,000 12 

95,000  to  100,000. II 

100,000  to  110,000 10 

1 10,000  to  1 20,000 o- 

120,000  to  130,000 8 

130,000  to  140,000 7 

140,000  to  150,000 6- 

150,000  to  160,000 5 

160,000  to  170,000 4 

170,000  to  180,000 i 

180,000  to  190,000 2 

190,000  to  200,000 i 

200,000  and  over o- 


50,000  to  55,000 2C 

NOTE — When  the  number  of  bacteri  per  cubic  centimeter  exceeds  the  local  legal  limit  th& 
score  shall  be  o. 

FLAVOR  AND  ODOR,  PERFECT  SCORE,  25 

Deductions  for  disagreeable  or  foreign  odor  or  flavor  should  be  made  according  to  conditions, 
found.  When  possible  to  recognize  the  cause  of  the  difficulty  it  should  be  described  under  Remarks. 

VISIBLE  DIRT— PERFECT  SCORE,  10 

Examination  for  visible  dirt  should  be  made  only  after  the  milk  has  stood  for  some  time  un- 
disturbed in  any  way.  Raise  the  bottle  carefully  in  its  natural,  upright  position,  without  tip- 
ping, until  higher  than  the  head.  Observe  the  bottom  of  the  milk  with  the  naked  eye  or  by  the 
aid  of  a  reading  glass.  The  presence  of  the  slightest  movable  speck  makes  a  perfect  score  im- 
possible. Further  deductions  should  be  made  according  to  the  amount  of  dirt  found.  When 
possible  the  nature  of  the  dirt  should  be  described  under  Remarks. 

FAT  IN  MILK— PERFECT  SCORE,  10 

POINTS  1  POINTS 

4.0  per  cent  and  over 10        i     3.4  per  cent. 


3.9  per  cent 9.8 

3.8  per  cent 9.6 

3-7  per  cent 9.4 

3.6  per  cent 9.2 

3.5  per  cent 9 

NOTE — New  York  State  legal  limit,  3%  fat. 


3.3  percent.  .  . 
3.2  per  cent.  .  . 
3.1  per  cent.  .  . 
3.0  per  cent.  .  . 


SOLIDS  NOT  FAT— PERFECT  SCORE,  10 


POINTS 

8.7  per  cent  and  over 10 

8.6  per  cent 9 

8.5  per  cent 8 

8.4  per  cent 7 

8.3  per  cent 6 

8.2  per  cent 5 

New  York  State  legal  limit,  11.5%  total  solids. 


8.1  per  cent 

8.0  per  cent 

7.9  per  cent 

7.8  per  cent 

Less  than  7.8  per  cent. 


POINTS 
4 
3. 


ACIDITY— PERFECT  SCORE.  5 


Less  than  0.2  per  cent 

0.2  per  cent  to  0.21  per  cent.  . 
0.21  per  cent  to  0.22  per  cent. 


POINTS 
S 
4 
3 


POINTS 

0.22  per  cent  to  0.23  per  cent 2 

0.23  per  cent  to  0.24  per  cent i 

0.24  per  cent  and  over o- 


BOTTLE  AND  CAP— PERFECT  SCORE,  5 


49 

EXERCISE   XVI 
JUDGING  CREAM 

i .  Judge  according  to  the  official  score  card,  the  samples  of  cream 
furnished.  If  enough  score  cards  are  not  available,  the  page  allotted 
to  notes  may  be  ruled  off  and  used  to  record  the  scores  of  the  different 
samples.  Before  beginning  the  work  of  this  exercise,  read  carefully 
the  directions  on  the  back  of  the  score  card  and  those  on  page. 

NOTE  : — Plating  milk  for  bacteria  involves  considerable  time  and 
labor.  If  it  is  impossible  to  plate  the  samples  judged,  the  bacteria 
score  may  be  called  perfect  and  the  milk  judged  according  to  the 
other  points  on  the  card.  This  will  not  give  the  true  quality  of  the 
milk,  but  it  will  give  the  student  practice  in  methods  of  judging  which 
is  the  prime  purpose  of  this  exercise.  This  is  particularly  true  in 
regard  to  detecting  flavors  and  odors. 


SCORE  CARD  FOR  MILK 


Place 


Class Exhibit  No . 


ITEM 

PERFECT 
SCORE 

SCORE 
ALLOWED 

REMARKS 

Bacteria  found  per  \  

35 

cubic  centimeter  / 
i  Flavor   

Flavor  and  odor 

25 

Odor  

Visible  dirt 

IO 

Fat 

2O 

Per  cent  found    

Acidity 

e 

Per  cent  found  

i  Cao 

Bottle  and  cap  

5 

(  Bottle    

Total    

IOO 

Exhibitor 


Address. 


Date, 


(Signed) . 

...191 

So 


Judge 


EXPLANATION  OF  SCORES 


BACTERIA  PER  CUBIC  CENTIMETER— PERFECT  SCORE,  35 


Less  than  400  

POINTS 
35 

55,000  and  less  than  60,000  .... 

POINTS 

ig 

400  and  less  than  700  

34.5 

60,000  and  less  than  65,000  .... 

18 

700  and  less  than  1,000  

34 

65,000  and  less  than  70,000  .... 

....            17 

1,000  and  less  than  2,000  .    . 

....       33.5 

70,000  and  less  than  75,000 

16 

2,000  and  less  than  3,000  

33 

75,000  and  less  than  80,000  .... 

15 

3,000  and  less  than  4,000  

32.5 

80,000  and  less  than  85,000  .... 

14 

4,000  and  less  than  5,000  

32 

85,000  and  less  than  90,000  .... 

5,000  and  less  than  6,000  

31.5 

90,000  and  less  than  95,000  .... 

12 

6,000  and  less  than  7,000  

31 

95,000  and  less  than  100,000  .  .  . 

7,000  and  less  than  8,000  

30.5 

100,000  and  less  than  110,000  .  .  . 

10 

8,000  and  less  than  9,000  

30 

110,000  and  less  than  120,000  . 

9,000  and  less  than  10,000  .... 

29 

120,000  and  less  than  130,000  .  .  . 

8 

10,000  and  less  than  15,000  

28 

130,000  and  less  than  140,000  .  .  . 

7 

15,000  and  less  than  20,000  

27 

140,000  and  less  than  150,000  .  .  . 

....            6 

20,000  and  less  than  25,000  

26 

150,000  and  less  than  160,000  .  .  . 

5 

25,000  and  less  than  30,000  

25 

160,000  and  less  than  170,000  .  .  . 

4 

30,000  and  less  than  35,000  

24 

170,000  and  less  than  180,000  .  .  . 

....            3 

35,000  and  less  than  40,000  .... 

23 

180,000  and  less  than  190,000  .  .  . 

2 

40,000  and  less  than  45,000  

22 

190,000  and  less  than  200,000  .  .  . 

I 

45,000  and  less  than  50,000  

21 

200,000  and  over  

o 

so.ooo  and  less  than  aa.ooo  .  . 

2O 

FLAVOR  AND  ODOR,  PERFECT  SCORE,  25 

Deductions  for  disagreeable  or  foreign  odor  or  flavor  are  made  according  to  conditions 
found.  When  possible  to  recognize  the  cause  of  the  difficulty  it  is  described  under  Remarks. 

VISIBLE  DIRT— PERFECT  SCORE,  10 

Examination  for  visible  dirt  is  made  only  after  the  milk  has  stood  for  some  time  un- 
disturbed in  any  way.  Raise  the  bottle  carefully  in  its  natural,  upright  position,  without  tip- 
ping, until  higher  than  the  head.  Observe  the  bottom  of  the  milk  with  the  naked  eye  or  by  the 
aid  of  a  reading  glass.  The  presence  of  the  slightest  movable  speck  makes  a  perfect  score  im- 
possible. Further  deductions  are  made  according  to  the  amount  of  dirt  found.  When  possible 
the  nature  of  the  dirt  is  described  under  Remarks. 

FAT  IN  CREAM— PERFECT  SCORE,  20 

If  20  per  cent  fat  or  above,  score  perfect.  Deduct  i  point  for  each  one-half  per  cent 
fat  below  20. 


ACIDITY— PERFECT  SCORE,  5 


0.2  per  cent  or  less 

0.21  per  cent  or  over  0.20. 
0.22  per  cent  or  over  0.21 . 


POINTS 
5 
4 
3 


POINTS 

0.23  per  cent  or  over  0.22 a 

0.24  per  cent  or  over  0.23 I 

Over  0.24  per  cent o 


BOTTLE  AND  CAP— PERFECT  SCORE,  5 

Bottles  should  be  made  of  clear  glass  and  free  from  attached  metal  parts.  Caps  should  be 
sealed  in  their  place  with  hot  paraffin,  or  both  cap  and  top  of  bottle  covered  with  parchment 
paper  or  other  protection  against  water  and  dirt.  Deductions  are  made  for  tinted  glass,  attached 
metal  parts,  unprotected  or  leaky  caps,  partially  filled  bottles,  or  other  conditions  permitting 
contamination  of  milk  or  detracting  from  the  appearance  of  the  package. 


52 

EXPLANATION   OF  EXERCISE  XVII 

The  main  purpose  of  a  bottle  filler  is  to  fill  several  bottles  at  the 
same  time  and  to  do  it  in  such  a  manner  that  there  will  be  the  smallest 
possible  amount  of  loss.  With  the  modern  filler  the  overflow,  air, 
froth,  etc.,  is  removed  from  the  bottle  by  means  of  a  small  tube  which 
connects  with  the  filler  tube  and  extends  upward  above  the  level  of  the 
milk  in  the  filler  tank.  In  cleaning  the  machine  it  is  necesslary  to 
scrub  the  inside  of  these  tubes  with  a  long  handled  brush  provided  for 
the  purpose.  Simply  rinsing  the  tube  is  not  sufficient.  The  filler 
tubes  usually  consist  of  two  parts,  one  which  fits  over  the  other,  and 
the  outside  tube  works  up  and  down  on  the  inside  tube  when  the  filler 
is  operated.  This  makes  it  necessary  for  the  tubes  to  fit  perfectly, 
and  great  care  must  be  taken  not  to  oughen  the  surfaces  of  these 
tubes.  In  some  cases  the  outside  and  inside  tubes  are  numbered  to 
correspond  so  that  the  operator  in  assembling  the  machine  may 
always  know  which  tubes  fit  one  another. 

The  end  of  the  outside  filler  tube  is  provided  with  a  rubber  gasket 
so  that  a  perfect  union  is  made  with  the  bottle  when  the  filler  is  in 
operation.  Bottles  with  chipped  and  broken  edges  'are  liable  to  cut 
the  rubber  gaskets,  and  unless  pains  are  taken  to  clean  them  they 
become  filled  with  milk,  rendering  them  unsanitary. 

Bottles  to  be  washed,  should  first  be  soaked  in  water  as  hot  as  the 
hand  will  bear,  to  which  has  been  added  some  washing  powder.  After 
washing  on  the  brushes,  the  bottles  should  be  rinsed  in  a  tank  of  clean, 
hot  water.  The  bottles  should  then  be  sterilized  by  means  of  live 
steam.  If  live  steam  is  not  available  they  may  be  placed  in  scalding 
hot  water.  It  is  best  not  to  place  the  crates  used  to  fill  bottles  inside 
the  sterilizer,  as  the  action  of  live  steam  soon  destroys  the  crates. 
Crates  suitable  for  this  purpose  may  be  made  from  ordinary  lumber. 
This  method,  however,  has  the  disadvantage  of  making  it  necessary  to 
transfer  the  bottles  to  the  filler  crates  at  the  time  of  bottling. 


53 

EXERCISE  XVII 
BOTTLING  MILK  AND  WASHING  BOTTLES 

1.  Place  all  loose  parts  of  the  filler  in  the  filler  tank  and  scald 
them  with  hot  water.     Note  whether  the  outside  and  inside  filler 
tubes  are  numbered  and  if  they  are,  be  sure  to  place  together  those 
bearing  the  same  number.     Fill  two  cases  of  quart  and  one  case  of 
pint  bottles.     Cap  one  case  of  quarts  with  the  standard  cap.     Ice  this 
crate  of  bottles  and  set  in  the  refrigerator.     Fill  one  case  of  Dacro 
bottles  (small  topped)  and  cap  them. 

2.  Remove  the  old  milk  from  the  refrigerator  and  pour  the  milk 
into  a  can.     Also  empty  all  bottles  of  milk  not  iced,  and  draw  off  into 
a  can  all  milk  in  the  fillers.     Wash  the  fillers,  using  small  brushes  for 
the  tubes.     Collect  all  dirty  bottles  and  wash  them.     Wash  the 
Dacro  bottles  with  the  foot  power  washer.     Place  the  washed  bottles 
in  the  sterilizer  and  turn  on  the  steam  before  leaving. 


54 
STUDENT'S  NOTES  AND   REPORT 


55 

EXPLANATION   OF  EXERCISE  XVIII 

The  clarification  of  milk  consists  in  removing  from  it  the  insoluble 
dirt.  The  modern  clarifier  does  this  by  means  of  centrifugal  force. 
The  dirt  found  in  milk  is  usually  heavier  than  the  milk  itself  and  the 
action  of  the  centrifugal  force  deposits  this  dirt  on  the  inside  of  the 
bowl.  Clarifiers  work  on  much  the  same  principle  as  do  separators, 
but  each  make  of  machine  has  special  features  tending  to  prevent 
separation.  Usually  a  clarifier  runs  slower  than  does  a  separator  of 
the  same  make  and  capacity.  In  a  separator,  the  inner  device  is  so 
constructed  as  to  spread  the  milk  in  a  thin  layer,  thereby  making  it 
possible  to  do  more  complete  separation. 

In  a  clarifier  the  milk  is  not  separated  in  as  thin  a  layer  and  only 
one  outlet  to  the  bowl  is  provided. 

The  different  construction  of  each  machine  will  be  studied  when 
the  machine  is  used. 

EXERCISE  XVIII 
EFFECT  OF  TEMPERATURE  ON  CLARIFICATION 

1.  Weigh  out  two  cans  of  milk  and  thoroughly  mix  them  by 
pouring  from  one  can  to  another  until  they  are  of  uniform  composi- 
tion. 

2 .  Clarify  one  can  of  milk  at  a  temperature  of  60°  F.  and  clarify 
the  other  at  a  temperature  of  85°  F.     Note  if  there  is  any  difference 
in  the  kind  and  amount  of  sediment  obtained. 

3.  Stain  some  of  the  sediment  obtained  from  each  clarification 
and  make  a  drawing  of  the  field.     In  case  there  is  no  microscopical 
difference  in  the  sediment  only  one  drawing  need  be  made. 


56 
STUDENT'S  NOTES  AND   REPORT 


57 

EXERCISE   XIX 

1.  For  use  with  the  clarifier,  weigh  a  can  of  milk  and  have  the 
temperature  as  near  60°  F.  as  possible.     Measure  out  100  cc.  of  the 
milk  into  a  measuring  cylinder,  both  before  and  after  clarification. 
Set  these  two  cylinders  aside  and  the  next  day  compare  the  cream  line 
on  the  two  samples.     Also  note  if  there  is  any  sediment  in  the  bottom 
of  either  cylinder,  and  if  so  compare  the  amount. 

2.  Run  the  milk  through  the  clarifier  and  keep  track  of  the  time 
required  for  the  process.     Note  the  kind  and  amount  of  sediment 
on  the  inside  of  the  bowl. 

3.  Stain  some  of  the  sediment  on  a  glass  slide  and  examine  it 
under  the  high  power  microscope.     Make  a  drawing  of  the  field. 

4.  Reclarify  the  same  amount  of  milk  and  compare  the  amount 
and  kind  of  sediment  with  that  obtained  in  the  first  clarification. 

5.  Make  a  drawing  showing  the  difference  between  the  inner 
device  in  a  separator  and  a  clarifier  of  the  same  make. 


58 
STUDENT'S  NOTES  AND  REPORT 


59 

EXPLANATION   OF  EXERCISE   XX 

In  sanitary  milk  production  it  must  be  kept  constantly  in  mind 
that  clean  milk  means  a  product  reasonably  free  from  germ  life.  It 
is  not  as  difficult  to  keep  germs  out  of  milk  as  is  commonly  supposed. 
There  are  a  few  simple  and  inexpensive  practices  which  if  carefully 
followed  will  do  much  in  aiding  the  dairyman  to  produce  a  good 
product. 

It  is  the  purpose  of  the  following  experiments  to  illustrate  the  value 
of  certain  dairy  practices  in  clean  milk  production  and  the  harmful 
effects  of  certain  other  practices  in  producing  clean  milk. 

In  performing  these  experiments  it  must  be  borne  in  mind  that 
anything  which  prevents  the  entrance  of  dust  and  dirt  into  milk 
is  an  aid  to  clean  milk  production.  On  the  other  hand,  any  disturb- 
ance which  causes  dust  particles  to  float  around  in  the  air  makes  it 
easily  possible  for  these  particles  to  enter  the  milk  while  it  is  being 
drawn  and  so  contaminate  it. 

The  use  of  the  small  top  pail,  and  wiping  the  udder  with  a  damp 
cloth  just  before  milking,  are  two  things  which  are  easy  to  do  and  are 
comparatively  inexpensive.  At  the  same  time,  they  are  exceedingly 
helpful  in  keeping  germs  out  of  milk. 

On  the  other  hand,  the  practice  of  feeding  hay  or  grain  just  before 
milking  stirs  up  a  dust  and  therefore  makes  it  possible  for  a  larger 
number  of  micro-organisms  to  enter  the  milk. 


EXERCISE   XX 
THE  VALUE  OF  THE  SMALL  TOP  PAIL  IN  CLEAN  MILK  PRODUCTION 

1 .  Carefully  sterilize  an  ordinary  wide  top  milk  pail  and  a  small 
top  or  covered  milk  pail. 

2.  Select  two  cows  standing  near  one  another  and  whose  flanks 
and  udders  are  alike  as  regards  the  amount  of  visible  dirt  on  them. 
Milk  one  cow  in  the  wide  mouth  pail  and  the  other  cow  in  the  small 
top  or  covered  pail. 

3.  Take  a  sample  of  milk  in  a  sterile  bottle  from  each  pail  and 
plate  the  samples  for  bacteria.     If  it  is  necessary  to  hold  the  samples 
for  any  length  of  time  before  plating,  the  bottle  should  be  set  on  ice. 

4.  After  the  colonies  in  the  plates  have  developed,  note  if  there 
is  any  difference  in  bacterial  content  of  the  milk  drawn  in  the  wide 
mouth  pail  and  that  drawn  in  the  small  top  or  covered  pail. 


6o 
STUDENT'S  NOTES  AND   REPORT 


6i 
EXERCISE   XXI 


1 .  Carefully  sterilize  two  small  top  or  covered  pails. 

2.  Select  two  cows  standing  near  one  another  whose  udders  and 
flanks  are  alike  so  far  as  amount  of  visible  dirt  is  concerned. 

3 .  Dampen  with  a  cloth  the  udder  and  flanks  of  one  of  the  cows 
and  milk  her. 

4.  Milk  the  other  cow  without  dampening  the  flank  and  udder. 
5r    In  a  sterile  bottle,  take  a  sample  of  milk  from  each  milking  and 

plate  the  milk  for  bacteria.  If  the  milk  cannot  be  plated  at  once,  the 
bottle  should  be  kept  on  ice.  Compare  the  number  of  bacteria  found 
in  the  milk  drawn  under  the  two  different  conditions. 


62 

STUDENT'S   NOTES  AND  REPORT 


63 

EXERCISE   XXII 

EFFECT  OF  FEEDING  HAY,  JUST  BEFORE  MILKING,  ON  THE  GERM 
CONTENT  OF  MILK 

1 .  Sterilize  two  small  top  pails  and  select  two  cows  whose  udders 
and  flanks  are  alike  as  regards  the  amount  of  visible  dirt  on  them. 

2 .  Milk  one  of  the  cows  and  take  in  a  sterile  bottle  a  sample  of  the 
milk  for  plating. 

3.  Before  milking  the  second  cow,  shake  two  or  three  forkfuls  of 
hay  near  where  she  stands.     Milk  the  cow  and  take  in  a  sterile  bottle 
a  sample  of  the  milk  for  plating. 

4.  Compare  the  number  of  bacteria  found  in  the  milk  drawn 
before  and  after  the  hay  was  shaken. 


64 
STUDENT'S   NOTES  AND   REPORT 


INDEX 

Bottle  fillers 52 

Bottling  milk 53 

Bottle  washing 53 

Clarification  of  milk 55,57 

Clarifier   55 

Cooling  Milk 21,25 

in  cans 21 

with  brine  and  ice 26,27 

with  conical  cooler 23 

Dairy  Utensils : 6 

Cleaning  of 5 

Construction  of 6 

Damp  Cloth 59,  61 

Use  in  clean  milk  production 61 

Dust 59 

Effect  of  in  clean  milk  production 59 

Milk 

Bottling 53 

Clean 5 

Cooling  of  milk . 21,25 

Judging  of 45,  46,  47 

Standardizing   8,13 

Pasteurization 16 

Flash  method 19 

Holder  method 17 

Salt 26 

Use  of  in  cooling  milk 26,  27 

Score  Card 31 

for  city  milk  plants  41 

for  cream 49 

for  Eairy  building 32 

for  milk 45 

Small  top  pail 59 

Efficiency  of 59 

Standardization    8,13 

Temperature  21 

of  milk  for  clarification 55 


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